In the art of container closures, it is well known to provide tamper-evident closures which are intended to reveal upon inspection whether the container has been previously opened. Such tamper-evident packaging considerations have recently assumed increased importance and have become the subject of considerable attention owing to various instances of intentional tampering with such consumer products as pain relievers and other medications, and foodstuffs.
One type of tamper-evident closure system which is in widespread use includes a screw cap closure for the mouth of a container, such as a bottle or jar, which screw cap includes an annular band attached to the lower extremity of the screw cap skirt by frangible bridges or along a score line. The band typically is formed to cooperate with the jar or bottle during first opening thereof to break the frangible bridges or score line and thus separate the band from the cap skirt. The broken score line or fractured bridges are intended to provide indication after subsequent closing of the container that the container has been previously opened.
Although such prior closure systems have usually served their intended purposes, they have nevertheless not offered of certain improvements disclosed hereinbelow which in general offer vastly improved assurance of separation of the band from the cap and enhanced visual tamper indication. In particular, one shortcoming of some such prior closures has been that the frangible portion may not break uniformly; that is, substantially at the same time. If the closure has a plurality of identical bridges as the frangible connection between the cap and the band, the bridges would be expected to break in a substantially uniform manner. The frangible bridges, however, are typically small in cross-sectional area, and even minor variations in the mold can cause substantial differences in the cross-sectional area and the strength of one or more bridges as compared with the remainder of the bridges. Thus, it is not unusual that one or more bridges in a tamper-evident closure may be substantially stronger or weaker than the remainder of the bridges. It may be seen, therefore, that the weaker bridges may break preferentially, and in such a case, the remaining bridges may not break as they were intended to do. If the remaining bridges do not break from the predetermined cooperation between the band and the bottle, the band will not separate from the cap and will undesirably be removed with the cap.
Prior closures, such as Rausing U.S. Pat. No. 4,109,814 and Ostrowsky U.S. Pat. No. 4,206,851, for example, are adapted to intentionally provide at least one bridge or connecting portion between the cap and the band to ensure that the band remains attached to the cap upon removal of the cap from the container. Such closures are not suitable or preferred, however, for all applications by closure users.
Even if all of the frangible portions, such as bridges, break as intended, prior closures have had an additional shortcoming in providing evidence of tampering. As noted heretofore, fracture of the frangible portion is effected by a portion of the band cooperating with a container portion to arrest movement of the band. The cooperating features may be provided by adapting the band with projections which engage indentations in the container whereby the band is restrained from rotational and/or vertical movement. Another popular cooperating feature comprises an inwardly projecting lip or lug on the band adapted to abut a corresponding outwardly projecting ridge or ledge on the container which arrests vertical movement of the band to effect breakage of the frangible portion. Regardless of means employed to fracture the frangible portion, lodgement of the band with the cooperating feature of the container to effect fracture has been a problem. It may be seen that if the band becomes lodged with the container when the frangible portion fractures, the cap and band will be in substantially the same spatial relationship after the cap is reengaged with the container as was their relationship before the frangible portion fractured. When this happens, only a close visual inspection of the closure will provide evidence of tampering. It is desirable, therefore, that after the band is separated from the cap, that the space between the cap and band upon reengagement of the cap and container be sufficient to clearly provide evidence of tampering. Fields U.S. Pat. No. 3,329,295 suggests a solution to the problem by adapting the closure and container dimensionally so that the band will fall freely around the container neck after separation from the cap. Because of conflicting tolerances in making closures and containers, such a scheme is difficult to control. Furthermore, the band may cock and hang up on the container rather than fall freely as it is intended to do.